1. Field of the Invention
The present invention relates to a lighting apparatus and, more particularly, to a lighting apparatus that emits light using microwave source energy.
2. Discussion of the Related Art
Generally, a microwave discharge lamp is an apparatus that applies microwaves to an electrode-less plasma bulb to generate visible light using microwaves at frequencies of hundreds of MHz to several GHz. The microwave discharge lamp has greater brightness and efficiency than an incandescent lamp and a fluorescent lamp, and is increasingly used. An electrode-less discharge lamp is a type of microwave discharge lamp that uses an inactive gas encapsulated in an electrode-less quartz globe (bulb). Almost all modern microwave discharge lamps are configured to emit a continuous spectrum of visible light through high pressure sulfur discharge.
A related art microwave discharge lamp includes a magnetron configured to generate microwaves, a bulb encapsulating a light emitting material to generate light using the microwaves, a resonator for resonation of the microwaves, in which the bulb is located, and a waveguide connecting the magnetron and the resonator to each other.
The light emission principle of the microwave discharge lamp will now be described in brief. Microwaves generated in the magnetron are transmitted to the resonator through the waveguide and, in turn, the microwaves introduced into the resonator excite the light emitting material in the bulb via resonation thereof within the resonator. As the light emitting material filling the bulb is converted into plasma, light is generated and emitted outwardly from the resonator.
An aperture for microwave transmission is provided between the waveguide and the resonator. The aperture is located in a resonance space within the resonator. When light is emitted by the bulb, the light may be introduced into the waveguide through the aperture, which may deteriorate luminous efficacy of the microwave discharge lamp.
In addition, simultaneously with introduction of light into the waveguide, radiant heat generated by the bulb may be transferred to the magnetron through the waveguide. The radiant heat raises a temperature of the magnetron, thus reducing magnetron lifespan.
Therefore, there is a demand for configurations to enhance luminous efficacy of the microwave discharge lamp and to increase magnetron lifespan.